High density integrated semiconductor devices present challenging design problems in that many connections have to be made to the device. The semiconductor chip with bond pads around it outer edges is placed in a lead frame and the bond pads are wire bonded to the lead frame fingers. Many times the fit between the device bond pads and the lead frame is not ideal. The device may be placed in a lead frame that was designed for another device.
In other instances, the device bond pad locations can not be optimized because of design restrictions. The corner wires in some designs are difficult to place because of the angle of the wire leaving the bond pad. Two adjacent wires may become too close to one another causing wire shorting after molding. This problem is particularly difficult in devices where two or more wires are grouped in the corner positions of the semiconductor chip.
Present methods of wire bonding attach a ball on the end of the bond wire to the bond pad, feed out sufficient wire to reach the lead frame finger and bond the wire to the lead frame finger in a direct path. Wires that are not straight, that lean or curved are usually suspect as defective.